When Hamlet exclaimed, "What a piece of work is a man," he cited, among other things, the wonderful fact that people are "noble in reason." As a species, we're justifiably proud of our ability to reason our way toward the truth.
Evolutionary theorists, of course, aren't content to admire -- they want to know why people are such good reasoners. In their new paper, "Why Do Humans Reason? Arguments for an Argumentative Theory" (just published in the journal Behavioral and Brain Sciences), cognitive scientists Dan Sperber and Hugo Mercier propose a new account of the origins of reasoning. Reasoning, they argue, actually didn't evolve to help us find the truth; it evolved to help us make, win, and evaluate arguments.
Sir Joshua Reynolds, Self-Portrait.
Sperber and Mercier start from the fact that we do plenty of thinking without articulating explicit reasons. We make choices, decisions, and inferences all the time, in a Gladwell-esque blink, without assembling a chain of reasons to back up our decisions. So the question is: What does reasoning add to our less elaborate systems for thinking and deciding? Some psychologists have argued that it helps us correct our intuitive mistakes; others, that it helps us project our thinking into the future.
Sperber and Mercier have a different proposal: The truth, they write, is simply that reasoning "enables people to exchange arguments." "The emergence of reasoning," they argue, "is best understood within the framework of the evolution of human communication." We don't need reasons to think, but to explain our thoughts to other people, especially to people who have no particular reason to trust us. In fact, even when we reason quietly, in our own heads, we do so "anticipating a dialogic context."
This view of reasoning suggests all sorts of things, some good, some bad. On the downside, it seems that "reasoning pushes people not towards the best decisions but towards decisions that are easier to justify." This is especially true in situations where there's no obvious, intuitive answer: If you can't decide between two equally palatable options, you're likely to choose the option for which you can generate the most arguments. On the other hand, the social nature of the reasoning process can push back against its rhetorical tendencies. Especially in groups, we become super-vigilant not only about others' reasoning, but about our own. If we reason in order to communicate, the authors argue, then we will reason better when we are communicating.
This, of course, wouldn't be news to Socrates -- it's why, in classrooms and courtrooms, we use the Socratic method. The point, though, isn't practical, but historical. Why are human beings today so noble in reason? Because of eons worth of social life. According to Sperber and Mercier, social life -- conversations, arguments, debates -- is the environment within which our reasoning skills have evolved.
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Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.